The invention relates to mixtures composed of silicon-containing coupling reagents, processes for their production, and also their use.
It is known that silanes can be used as coupling agents. By way of example, aminoalkyltrialkoxysilanes, methacryloxyalkyltrialkoxysilanes, polysulfanealkyltrialkoxysilanes, and mercaptoalkyltrialkoxysilanes (E. P. Plueddemann, “Silane Coupling Agents”, 2nd edn. Plenum Press 1982) are used as coupling agents between inorganic materials and organic polymers, as crosslinking agents, and as surface modifiers.
These coupling agents or bonding agents form bonds both to the filler and to the elastomer, thus bringing about good interaction between the filler surface and the elastomer.
It is moreover known that the use of commercially available silane coupling agents (DE 22 55 577) having three alkoxy substituents on the silicon atom leads to liberation of considerable amounts of alcohol during and after binding to the filler. Since trimethoxy- and triethoxy-substituted silanes are generally used, considerable amounts of the corresponding alcohols—methanol and ethanol—are liberated (Berkemeier, D.; Hader, W.; Rinker, M.; Heiss, G. Mixing of silica compounds from the viewpoint of a manufacturer of internal mixers. Gummi, Fasern, Kunststoffe (2001), 54(1), 17-22).
It is moreover known that methoxy- and ethoxy-substituted silanes are more reactive than the corresponding long-chain alkoxy-substituted silanes, and therefore can bind more rapidly to the filler, and for technical and economic reasons it has therefore been impossible hitherto to forgo the use of methoxy and ethoxy substituents. DE 10137890, JP 62-181346, De 3426987, and EP 0085831 disclose various mercaptosilanes.
DE 102005032658.7 moreover discloses polyether-substituted mercaptosilanes. These silanes are synthesized by reacting alkoxysilanes with an alkoxylated alcohol, with catalysis.
DE 102005052233 discloses a process for the production of organosilanes by reaction of (haloorganyl)alkoxysilanes with hydrous sulfurization reagents.
JP 2005232354 moreover discloses the use of mercaptosilanes with partial esters of maleic anhydride with (poly)oxypropylene derivatives in rubber mixtures.
EP 1672017 discloses rubber mixtures comprising rubber, fillers, if appropriate further rubber auxiliaries, and at least one mercaptosilane.
Disadvantages of the known alkoxy-substituted and/or alkylpolyether-substituted mercaptosilanes having long-chain alkoxy groups, when used in rubber mixtures, are poor processing properties and/or dynamic properties accompanied by reduced alcohol emission or good processing properties and/or dynamic properties accompanied by increased alcohol emission.
It is an object of the present invention to provide coupling reagents which in filler-reinforced rubber mixtures lead to at least identical processing properties and/or at least identical dynamic properties in comparison with known coupling reagents, e.g. alkylpolyether-alcohol-substituted mercaptoorganylsilanes, where this is accompanied by reduced alcohol emission.